Hints of New Physics Crop Up at LHC

Preliminary findings from CERN’s Large Hadron Collider may have uncovered experimental evidence for physics beyond the Standard Model. Data from the CMS experiment is showing significant excesses of particles known as leptons being created in triplets, a result that could be interpreted as evidence for a theory called supersymmetry.

The findings, presented during a talk Oct. 19 at a conference dedicated to LHC searches for new physics, have piqued the interest of some members of the field.

“This is clearly something to watch closely over the coming months,” physicist Matt Strassler wrote on his blog. That’s because these particular triple lepton signatures are sometimes called the “golden channel” to revealing supersymmetry, a theoretical model that posits the existence of a heavier partner to all known subatomic particles in order to solve certain problems with the Standard Model.

The most familiar lepton is the humble electron, though other, more exotic particles such as muons and taus also fall in this category. Producing a single one of these subatomic particles in the proton-proton collisions at the LHC is relatively rare, and generating two or even three at a time is even more unusual. Certain interactions predicted under supersymmetry could enhance the odds of triple lepton events, so seeing excesses is reason to raise some eyebrows.

Yet searching for triplets of leptons is a complex task. As with many results from the LHC, the finding is subtle and could potentially be overturned with further data. Therefore, the CMS team is cautious, stressing that all their observed data is consistent with background expectations and that there isn’t definitive proof of new physics yet.

“We do our best, applying different independent approaches and make sure they all give consistent results, but we need to make more cross checks before claiming any inconsistency with the Standard Model,” wrote physicist Fedor Ratnikov of the Karlsruhe Institute of Technology in Germany, who presented the CMS results at the conference, in an email.

Processes other than supersymmetry could also account for the triple lepton surplus. But if the result keeps appearing, or the ATLAS experiment confirms the finding, it could be the start of something interesting.